A hot-melt adhesive, which is an adhesive melted by heat to be applied, has been increasingly used as an environmentally friendly adhesive due to less emission of volatile organic solvents. Recently, in addition to the less emission of the volatile organic compounds which are harmful to human body, efforts to prevent global warming are systematized to protect environment. As a part of the global efforts from various countries, it is preferably demanded to use resins having less emission of carbon dioxide, that is, having a small value of life cycle assessment (LCA). Polycarbonate is prepared using carbon dioxide as a raw material, and has an LCA value of about 1.3, which is remarkably smaller than that of the other polymer resin such as polyethylene or polypropylene. Therefore, a method of decreasing carbon emission quantity in process of preparing a hot-melt adhesive by preparing the hot-melt adhesive using the polycarbonate resin may be provided.
It is general that the existing and general hot-melt adhesive is prepared by containing thermoplastic polymers such as olefin-based copolymer, and the like, as a base polymer, and adding various waxes such as tackifiers or viscosity modifiers thereto. As the base polymer, olefin-based copolymers such as ethylene-vinyl acetate copolymer, ethylene acrylic ester copolymer, ethylene vinyl acetate, and the like, have been widely used due to advantages such as excellent flexibility and cheap cost.
In addition, as the tackifiers improving adhesion, natural resins such as rosin-based resins, terpene-based resins, and the like, and derivatives thereof, and petroleum resins have been largely used, and as waxes decreasing viscosity, petroleum-based waxes, mineral waxes such as coal, low-molecular weight polyethylene waxes, and the like, have been largely used.
The hot-melt adhesive has been widely used in various fields such as automobile, packaging, structural material, electronic material, and the like. However, in the case in which the olefin-based copolymer having small polarity is used as a base polymer, or a surface coating is performed with silicon, wax, or the like, adhesion is not sufficient, and a holt-melt adhesive using a thermoplastic rubber as a base polymer has excellent heat resistance and cold resistance but high viscosity, thereby causing a problem in that workability is decreased.
In addition, in the case in which excessive amount of plasticizers are used in order to reinforce cold resistance or elasticity, compatibility with a base resin is not favorable to occur a phase separation at a workable temperature, thereby causing a bleeding phenomenon, whereby adhesion is reduced, and sufficient strength and flexibility may not be shown at a low temperature.
US Patent Application Publication No. 2011-0229721 (Patent Document 1) discloses a hot-melt adhesive containing an ethylene-vinyl acetate copolymer, a styrene block copolymer, a tackifying resin, and a plasticizer. However, the existing hot-melt adhesive has adhesion with respect to various materials, but does not have adhesion as sufficient as epoxy or urethane adhesive, and has low flexibility and adhesion at a low temperature, thereby having a limitation to be used as an adhesive according to various usages.
In addition, U.S. Pat. No. 5,973,056 (Patent Document 2) discloses a hot-melt adhesive having excellent heat resistance and cold resistance by containing an epoxy-modified block copolymer, a paraffin wax, a tackifier, and an antioxidant, wherein heat resistance and cold resistance are slightly improved due to excellent compatibility between the epoxy-modified block copolymer and the paraffin wax, but mechanical strength and adhesion as the hot-melt adhesive used for various objects are not sufficient.
Therefore, research into an environmentally friendly hot-melt adhesive having an improved cold resistance having excellent strength and flexibility and high adhesion even at a low temperature, and high energy efficiency at the time of being applied, without using a solvent according to adhesion, has been conducted.